Differentiation Question 454

Question: If $ f(x)=x+2, $ then $ f’(f(x)) $ at x = 4 is

[DCE 2001]

Options:

A) 8

B) 1

C) 4

D) 5

Show Answer

Answer:

Correct Answer: B

Solution:

$ f(x)=x+2 $

Therefore $ {f}’(x)=1 $

\ $ {f}’(f(x))={f}’(x+2)=1 $ at $ x=4 $ .